A method and a device for transmitting a signal by using a polar code are provided. The method includes generating a first codeword by applying the polar code to an input signal, dividing the first codeword into a plurality of partial vectors, allocating a shaping bit to the input signal when at least one of the plurality of partial vectors does not satisfy a preset Hamming weight condition, generating a second codeword by applying the polar code to the input signal to which the shaping bit is allocated, and transmitting a signal based on the second codeword.